<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    body { text-align: center; }
    img { width: 205px; height: 200px; margin-bottom: 2px; }
    button { display: block;  margin: 0 auto; }
  </style>
</head>
<body>
  <div>
    <img  src="images/1.jpg" title="火锅">
    <button>选择</button>
  </div>
  <script>
    var btn = document.querySelector('button'); // 获取button元素
    var img = document.querySelector('img');    // 获取img元素
    btn.onclick = function () {
      img.src = 'images/selected.jpg';
    };
  </script>
</body>
<html>